Granulator for granulating plastic strands

ABSTRACT

The granulator has a hollow knife cylinder with knife edges extending from end to end. The plastics strands are fed in transversely to the longitudinal axis of the cylinder while the cylinder and strands are moved relative to one another longitudinally of the cylinder. The bearing system of at least one end of the cylinder is disposed within the cylinder. At this end, the cylinder is provided with an inclined surface projecting beyond the cylinder in the axial direction; the imaginary elongation of this surface meets or intersects the end of the path of the knife edges.

United States Patent [191 Fritsch [451 May -7, 1974 GRANULATOR FORGRANULATING PLASTIC STRANDS [76] Inventor: Rudolf Paul Fritsch, GoslarerStrasse 58, 7 Stuttgart 31, Germany [22] Filed: Apr. 17, 1973 [21] Appl.No.: 351,967

[30] Foreign Application Priority Data Apr. 22, 1972 Germany 2219785[52] US. Cl 83/356.3, 8.3/356, 83/906 [51] Int. Cl B23d 25/00 [58] Fieldof Search 83/355, 356, 356.3, 349,

[56] References Cited UNITED STATES PATENTS 2,798,550 7/1957 Kubodera83/356 Primary Examiner-J. M. Meister 57 ABSTRACT The granulator has ahollow knife cylinder with knife edges extending from end to end. Theplastics strands are fed in transversely to the longitudinal axis of thecylinder while the cylinder and strands are moved relative to oneanother longitudinally of the cylinder. The bearing system of at leastone end of the cylinder is disposed within the cylinder. At this end,the cylinder is provided with an inclined surface projecting beyond thecylinder in the axial direction; the imaginary elongation of thissurface meets or intersects the end of the path of the knife edges.

4 Claims, 4 Drawing Figures GRANULATOR FOR GRANULATING PLASTIC STRANDSThe invention relates to a granulator for granulating plastics strands,provided with a hollow knife cylinder, journalled at both ends andhaving knife edges extending from end to end. The longitudinal axis ofthe knife cylinder extendings approximately perpendicularly to thein-fed plastics strands, and the knife cylinder and plastics strandstraversed relative to each other longitudinally of the cylinder axis.

The prior art discloses a granulator of the kind described above whichis traversable on rails transversely to the in-fed plastics strands andaccordingly, when operation is started, is moved into the path of theplastics strands, which are delivered by a cooling plant. Relativelylarge bearing houses are provided on both ends of the knife cylinder inknown granulators, these bearing housings causing difficulties in termsof motion into the path of the in-fed plastics strands because thesestrands initially strike the bearing housings instead of engaging theknife cylinder. This also applies to a slidable granulator which hasalso been proposed and incorporates two knife cylinders which arealternately operated.

It would therefore be desirable to provide a granulator which could bemoved laterally into the path of the in-fed plastics strands withoutobstructing the feed of such strands, thus ensuring a reliable start ofthe granulating operation.

This is achieved by disposing the bearing system of at least one end ofthe knife cylinder in the interior of the cylinder and providing thisend-face of the knife cylinder with an inclined surface which extendsbeyond the knife cylinder in the axial direction and forms an acuteangle with the plastics strands so that their imaginary elongation meetsthe ends of the knife edges of the knife cylinder or intersectstherewith.

On the one hand, no bearing housing obstructs the feed of the strandswhen the granulator is moved into the path of the plastics strands and,on the other hand, these strands are deflected by the inclined surfaceso that they are reliably cut by the knife edges at the end of the knifecylinder and the process of granulation may start without complications.The application of the basic idea of the invention is particularlyadvantageous in respect of the known granulator with two knifecylinders, the inclined surfaces being then provided on the inwardlyfacing end-faces of the two knife cylinders.

To ensure that the plastics strands, which are not particularlyresistant to bending because of their small cross-section, are guided(with respect to the vertical direction) so that they assume the optimumposition with respect to the cutting edges of the knife cylinder asrequired for end granulation it is advisable to form the inclinedsurface by providing a progressively deepening groove in one end platewhich closes the end-face of the knife cylinder or its bearing system,the said groove extending in the direction of the in-fed plasticsstrands. The lower flank of the groove then functions as a guide for theplastics strands. To the same end, it is also advisable if the lowerflank of the groove is in alignment with a support for the plasticsstrands disposed upstream of the knife cylinder. A support of this kindis already provided in conventional granulators.

In a preferred embodiment, the bearing housing on the end of the knifecylinder which has the inclined surface is provided with an outrigger orextension in the form of a circular section or annular circular sectorfor mounting the bearing system on a machine frame, so that the mountingmeans for the bearing systems which have been displaced into theinterior of the knife cylinder do not obstruct the feed of the plasticsstrands. This outrigger may be constructed shallower than half theheight of the knife cylinder so that it does not obstruct the plasticsstrands which are fed in approximately into the horizontal median planewhen the grandulator is moved into the path of the strands.

The granulator may of course also be fixedly disposed and the plantwhich delivers the plastics strands to the granulator, that is to sayusually the cooling plant, may be slidably constructed, but it isusually simpler to provide a fixed cooling plant and a slidablegranulator.

The invention will. be described further, by way of example only, withreference to the accompanying drawings, in which:

FIG. 1 is a diagrammatic side view of a plant for producing plasticsgranulate;

FIG. 2 is a section through the essential parts of the granulator ofthis plant, taken along the line 2-2 of FIG. 1;

FIG. 3 is a side view of the granulator and FIG. 4 is a section throughpart of the granulator, taken along the line 4-4 of FIG. 3.

FIG. I shows in diagrammatic form an extruder head 10 from the bottom ofwhich a row of plastics strands are extruded. These pass through acooling plant 12 filled with water, through which the plastics strandsare conveyed by means of conveyor belts 14. A pair of delivery rollers16 is disposed at the right-hand end of the cooling plant as seen inFIG. I; this roller pair delivers the solidified plastics strands to agranulator 18.

The drive of the granulator 18 is housed in a motor casing 20, whichsupports a machine frame 22. The entire granulator is carried by wheels(not shown) running on rails 24, so that it is traversableperpendicularly to the plane of the drawing (FIG. 1). A knife cylinder26 is journalled on the machine frame 22 so as to be rotatable about anaxis which is perpendicular to the plane of the drawing (FIG. 1); theknife cylinder is driven-via a transmission (not shown) by the motor inthe motor casing 20 and is covered by a hood 28. The granulated plasticspasses through a discharge trough 30 into a collecting container 32.

FIG. 2 shows the detailed construction of the granulator in the regionof the knife cylinder 26. Two bearing systems 34 and 36 are mounted onthe machine frame 22, the shaft 38 of the knife cylinder26 beingrotatably journalled in these bearing systems. The knife cylinder shaft38 carries two discs 40 and 42 on which a support cylinder 44 ismounted. The cylinder 44 supports a knife cylinder 46 having cuttingedges 48 which extend longitudinally as far as the ends of the knifecylinder.

The left-hand bearing system 34 of the shaft 38, as viewed in FIG. 2 isconventionally constructed and it is therefore not necessary to describeit in detail. The right-hand bearing system 36, which comprises abearing housing 50 in several parts and a rolling bearing 52, isdisposed substantially within the knife cylinder 46 so that merely abearing housing cover 54 and a bearing housing collar 56 extend slightlybeyond the knife cylinder 46. As may be clearly seen by reference toFIGS. 2 and 4, the bearing housing collar 56 is provided with a shell 60for mounting the bearing 36 on the machine 70 (see FIGS. 3 and 4) whoselower flank 70a is in alignment with the support surface 64a of theanvil 64 and whose base 70b extends at an angle so that plastics strands80 (shown .in dash-dot lines in FIG. 4) bearing on the base 70b arereliably gripped and cut off by the ends of the cutting edges 48 whenthe granulator is moved from left to right (FIG. 2) into the path of theplastics strands which are advanced by the delivery rollers 16 (FIG. I),thus initiating the process of granulating. The bearing housing 50 ofthe illustrated embodiment is constructed so that its collar 56 also hasa groove 82, which serves as a guide groove; its lower flank 82a is alsoin alignment with the support surface 64a.

The grooves 70 and 82 therefore prevent the plastics strands frombearing flat against the end-face of the knife cylinder 46, where theycould not be engaged by the cutting edges 48 when the granulator ismoved into the path of the plastics strands. It can also be seen fromFIG. 3 that the shell 60 is not so tall as to obstruct the feed of theplastics strands when the granulator is moved into their path from theside.

I claim:

1. A granulator for granulating plastics strands, comprising a hollowknife cylinder, having a bearing system at each end and havinglongitudinal knife edges extending from end to end, the plastics strandsbeing fed in transversely to the longitudinal axis of the knife cylinderwhile the knife cylinder and plastics strands are movable relative toeach other longitudinally of the said axis, the bearing system of atleast one end of the knife cylinder being disposed in the interior ofthe cylinder, the end-face of the knife cylinder at the said end beingprovided with an inclined surface which projects beyond the knifecylinder in the axial direction and forms an acute angle with radialdirection, the imaginary elongation of the inclined surface meeting'orintersecting the end of the path of the knife edges of the knifecylinder, whereby the plastics strands come successively into the pathof the knife edges without being obstructed by the bearing system.

2. A granulator as claimed in claim I, in which the said inclinedsurface is formed by the base of a transverse groove in the saidend-face, the depth of the groove increasing in the radial direction.

3. A granulator as claimed in claim 2, further comprising a support forplastics strands entering the granulator, the groove having a flankwhich is in alignment with the support.

4. A granulator as claimed in claim I, in which the said bearing systemhas a casing including an extension for mounting the bearing on amachine frame.

1. A granulator for granulating plastics strands, comprising a hollowknife cylinder, having a bearing system at each end and havinglongitudinal knife edges extending from end to end, the plastics strandsbeing fed in transversely to the longitudinal axis of the knife cylinderwhile the knife cylinder and plastics strands are movable relative toeach other longitudinally of the said axis, the bearing system of atleast one end of the knife cylinder being disposed in the interior ofthe cylinder, the endface of the knife cylinder at the said end beingprovided with an inclined surface which projects beyond the knifecylinder in the axial direction and forms an acute angle with radialdirection, the imaginary elongation of the inclined surface meeting orintersecting the end of the path of the knife edges of the knifecylinder, whereby the plastics strands come successively into the pathof the knife edges without being obstructed by the bearing system.
 2. Agranulator as claimed in claim 1, in which the said inclined surface isformed by the base of a transverse groove in the said end-face, thedepth of the groove increasing in the radial direction.
 3. A granulatoras claimed in claim 2, further comprising a support for plastics strandsentering the granulator, the groove having a flank which is in alignmentwith the support.
 4. A granulator as claimed in claim 1, in which thesaid bearing system has a casing including an extension for mounting thebearing on a machine frame.